diff --git a/simulation.lisp b/simulation.lisp
index 3065ceb..e19e5e7 100644
--- a/simulation.lisp
+++ b/simulation.lisp
@@ -38,3 +38,17 @@
   (with-slots (running simulation-thread) sim
 	(setf running nil)
 	(sb-thread:join-thread simulation-thread)))
+
+(defmacro define-simulation (name &key lagrangian coords render start params)
+  `(progn
+	 (defclass ,name (simulation)
+	   ()
+	   (:default-initargs :start ',start :params ',params))
+	 (defmethod update ((sim ,name) dt)
+	   (with-slots (state params) sim
+		 (setf state ,(let ((eqns (hamilton-eqns lagrangian coords)))
+						(update-body eqns coords params)))))
+	 (defmethod render ((sim ,name))
+	   (with-slots (state) sim
+		 (let ,(mapcar (lambda (q) `(,q (getf state ',q))) coords)
+		   ,render)))))